Starting in the early 1980s, caller-identification signals, also known as caller-id, have been transferred from phone systems (e.g. Plain Old Telephone Service or POTS) to station equipment (e.g. land-based telephones). There are/were several versions and standards of caller-identification throughout the world. Currently, in the United States, the caller-identification information (e.g. calling number and calling name, if available) are transmitted to a subscriber's station equipment (e.g. phone) during the interval between the first ring and the second ring. The calling party's information is transferred through the phone system on a signaling plan called SS7 (Signaling System 7) until it reaches the subscriber's provider phone switch where it is encoded in either Single Data Message Format (SDMF), which provides the caller's telephone number and the date and time of the call or Multiple Data Message Format (MDMF) which provides the caller's name, telephone number and the date and time of the call. The data is modulated using, for example, a modulation technique similar to the Bell 202 standard used for early modems.
A similar system and signaling plan is implemented by cable-based phone systems such as Voice Over Internet Protocol (VoIP), although the information is signaled throughout the network differently, the same signaling methods are used between the phone/cable Analog Phone Adapter (APA) and the station equipment (phone) in order to permit attachment of legacy phones to an RJ-11 jack of the Analog Phone Adapter.
Of further interest is the actual ring system used by phone systems. Phone systems signal ringing with a high-voltage pulsed DC or AC signal. In North America, the high-voltage signal is around 90 volts at 20 Hz while in Europe, the high-voltage signal is 60-90 volts at 25 Hz. In North America, the cadence is 2-4, or two seconds of ring voltage followed by four seconds of silence. It is possible to use the ring signal for powering a device by charging a capacitor or similar charge device during the ring interval then using power from the capacitor to power other circuitry.
The caller-identification and ring signal are transferred from the phone system or APA though a two-wire interface known as Tip and Ring, usually through cabling connected with a standard phone plug/jack known as RJ-11. Station equipment such as phones, computers, televisions that are directly connected to the Tip and Ring are able to receive the caller-identification and ring signals and use them to initiate a ring sound and/or display the caller information on a display. Such station equipment was required to be directly connected to the Tip and Ring interface.
What is needed is a system that will capture the caller-identification information from the Tip and Ring and transfer the caller-identification information to a system such as a television where it is displayed.